This invention relates generally to crop harvesting and threshing machines, more commonly known as combines, and more particularly to the infeed housing attached to the front of the base unit of the combine which is used to transfer the crop material from the harvesting attachment or header upwards into the base unit where the threshing operation occurs. Specifically, the invention is concerned with control apparatus which responds to an input signal from the stone detecting apparatus by sending an output signal to an actuator cooperable with the drive unit for the crop elevator within the infeed housing to disengage the drive to the crop elevator while permitting the considerable inertial force within the elevator to dissipate itself.
In the prior conventional types of combines using a transverse threshing cylinder, stone traps were routinely provided to separate out large hard objects or stones that generally were greater than three or four inches in size. The stone traps provided in the conventional combines were utilized generally in two types of stone ejecting systems.
The passive type of stone ejecting system employed a stone trap with a space or gap between the top of the crop elevator or conveyor within the infeed housing and the base unit threshing apparatus. In this type of an ejecting system hard objects or stones were conveyed upwardly along with the crop material from the header through the infeed housing towards the threshing apparatus. When the crop material passed over the gap, stones by their very weight would fall down through the gap into the stone trap. Those stones that were carried along with the crop material past the stone trap were passed into contact with the threshing cylinder, which generally was rotatably mounted transversely to the longitudinal axis of the combine. If the hard objects or stones were of sufficient size so that they would not easily pass between the threshing cylinder and the threshing concaves, they would be thrown backwardly by the rotation of the cylinder into the gap or space. Thus, this particular cooperation between the threshing cylinder and the stone trap created an almost natural stone ejecting system for conventional combines. Even if a stone did pass into the threshing cylinder it made only one pass about the cylinder and across the underlying concave, usually doing minimal damage to the threshing apparatus before it was passed on through and ejected from the combine.
The second type of stone ejecting system generally employed an active system which utilized some sort of an electronic sensor, such as an acoustic transducer typically in the form of a piezoelectric disc mounted in a sensing plate, in conjunction with a stone trap. The electronic sensor responded to the characteristics of the sound, such as the amplitude and frequency, that an impacting stone generated in the sensing plate. This signal would then be transferred through an electronic circuit that filtered out the range within which the amplitude and frequency was characteristic of stones. Within this characteristic spectral range the electronic circuit automatically activated a latch releasing mechanism on a door along the bottom of the infeed housing that would pivot open to permit the stones or hard objects to be ejected from the feeder house, along with a small amount of crop material.
This latter or active type of sensing system utilizing a latched trap door that was automatically opened upon impact of a stone or stone-like object against the sensing plate was an appreciable step forward in stone detecting and ejecting technology. However, because the stone or stone-like objects were generally passed along the predetermined path with the crop material, quite frequently when the stone trap door was opened the stone or hard-objects continued to move along with the crop material and passed over the opening created by the lowered trap door. Frequently, the detected stones would still pass upwardly from the infeed housing into the threshing apparatus, where it would pass with the crop material about the threshing concave and the threshing cylinder. Again, because it was only a single pass of crop material about a portion of the conventional transverse threshing cylinder and across a relatively narrow strip of concave, detected but unejected stones still caused minimal damage to the combine.
An alternate type of active stone ejecting system utilized a pinch roll rotatably mounted in the infeed housing at a predetermined distance above the trap door. When a stone of sufficient size was carried by the crop elevator between the pinch roll and the trap door into compressive engagement therewith, the rotation of the pinch roll exerted a downward force through the stone against the trap door. The trap door was spring loaded closed so that above a predetermined pressure the door would be forced open, thereby causing the stone to be directed downwardly and out of the infeed housing through the opening created by the opened trap door. An obvious drawback to this system was the fact that large, but relatively flat stones or stone-like objects capable of passing between the pinch roll and the trap door were ingested into the combine where they could still damage the operating components.
The advent of rotary or axial flow type of combines with single or multiple threshing and separating rotors utilized in an orientation where the longitudinal axis of each rotor is either parallel or transverse to the longitudinal axis of the combine presented a greater need for more effective stone eliminating or ejecting systems. This increased need stems from two principal facts. Axial flow combines generally do not have a transverse threshing cylinder at the top of the infeed housing to throw or direct stones or other damage inducing objects back into the stone trap. They also pass the crop material about the periphery of each rotor as many as five or six times during threshing and separation as the crop material progresses axially along the length of each rotor.
An improved electronic stone or stone-like object detecting system was developed, as shown and described in copending U.S. patent application Ser. No. 109,932, filed Jan. 4, 1980 and assigned to the assignee of the present invention, utilizing a sensing plate that is positioned transversely across the bottom of the infeed housing astride the path of crop flow from the header to the base unit of the combine. In this type of a system the reaction time for the opening of the trap door is relatively short and, because the crop material in an axial flow combine makes multiple passes about the rotor as it is transferred along the length of the concave during the threshing and separating cycle, elimination of detected stones and stone-like objects becomes more critical. A stone or stone-like non-frangible object passing through an axial flow type of combine is more apt to damage the entire length of the concaves, which with their rasp or rub bars cooperate with the rotors to thresh the crop material. In marked contrast, a stone passing through a conveying crop material from the header to the threshing and separating apparatus while permitting the considerable inertial movement in at least the crop elevator to dissipate itself without damaging the drive system thereto.